Cohensioned silk yarn and silk knit cloth

ABSTRACT

The present invention provides a yarn which is a covering yarn consisting of only silk and a yarn containing sericin. A cohesioned silk yarn is obtained by using raw silk, as a core yarn, with sericin in swollen state in reeling process at reel speed of 20 to 100 m/min, and by covering a raw silk in said reeling with a wild silk yarn, and by fusion-bonding a raw silk and a wild silk yarn by sericin. Said cohesioned silk yarn can be subjected to automatic knitting.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for producing a cohesioned silk yarn wherein both a core yarn and a covering yarn are made of silk and both are bonded by sericin, along with said cohesioned silk yarn and products thereof.

2. Prior Art

When a raw silk is twisted, yarns are bundled and stabilized and provides an easy handling, therefore, gives a good weaving and knitting process, on the contrary, the twisting makes a yarn restricted and harder, therefore, the products from them provide a sturdy cloth but relatively hard feeling. On the other hand, when the non-twisted raw silk is used after degumming to obtain a cloth with soft feeling, yarns are scattered and thus cannot be utilized for the degummed woven fabric or knit fabric. It may be applied to the post-degumming woven fabric but provides unsuitable commercial products due to friction and irregular fuzz.

In the above circumstance, many proposals have been made on composite yarns having composite structure of a core yarn and a sheath yarn mainly made of raw silk to compensate the above weakness and improve property or feeling while maintaining characteristics of raw silk.

First of all, such a composite yarn has been proposed that a chemical fiber is combined with a raw silk, wherein a chemical fiber is immersed into a hot water tank at or near boiling point without tension just before the combination with raw silk and then is subjected to shrinkage (JP-A-60-194106). Further, a composite yarn obtained by enveloping a core of an elastic yarn such as a polyurethane filament yarn having elongation at break larger than 3 times elongation of a silk yarn, with a substantially non-twisted silk yarn and then adhering a silk yarn to the elastic yarn by sericin (JP-A-4-194043) and a commingled yarn of polyester and silk, wherein bave of a silk filament is entangled around a specific polyester filament and a part of the contact area of both filaments is partially adhered by sericin (JP-A-63-235536), is known. However, in any of these composite yarns, a chemical and synthetic yarn is exposed on the yarn surface with a silk yarn, which inhibits the sufficient expression of hygroscopicity, skin feeling and the like inherent to raw silk. In the above circumstance, the present inventors have proposed a non-twisted silk yarn, which is produced by covering non-twisted raw silk with a chemical and synthetic yarn having a shrinkage rate in hot water larger than said raw silk by 9 to 12% and fineness smaller than raw silk, subsequently inverting alignment of a chemical and synthetic yarn and raw silk by shrinkage in hot water and a non-twisted silk yarn evaginates on the yarn surface (JP-A-2002-180344). This yarn is bulky and soft and can be subjected to fabrication of knit or woven fabric in high speed; however, any of the above-described composite yarns poses various problems in use derived from not being composed of only silk but including foreign material.

BRIEF SUMMARY OF THE INVENTION

It is the object of the present invention to provide a covering yarn composed of only silk and products thereof, wherein a covering yarn has conquered the above-described defects, and contains sericin which, in usual case, is removed by degumming, and therefore has the various effects to skin due to presence of sericin, and moreover can provide the knit products by using a non-sewing automatic knitting machine.

The present inventors have extensively studied a way to solve the above-described problems and found that the above objective can be attained by covering bave (a domesticated silk yarn) in reeling process with a degummed wild silk yarn in the condition not to lower the elongation of bave.

That is, the present invention aims at producing a cohesioned silk yarn, wherein, as a core yarn, a raw silk is used where sericin is under the swollen state in reeling process at reel speed of 20 to 100 m/min, and a wild silk yarn is covered in the condition not to lower elongation of said raw silk, and a raw silk and a wild silk yarn are bonded by sericin. The covering is preferably executed 200 to 600 times/m. A cohesioned silk yarn thus obtained is composed of swollen raw silk as a core yarn and by covering said raw silk with a wild silk yarn, and a raw silk and a wild silk yarn are bonded by sericin, and a degummed tussah silk yarn can be used as a wild silk yarn. A cohesioned silk yarn according to the present invention can be subjected to automatic knitting to provide knit products.

A cohesioned silk yarn of the present invention is a covering yarn composed of only silk and is a yarn not only superior in skin feeling, heat retaining property and water absorption inherent to silk but also has, due to containing sericin, function such as oxidation resistance, antibacterial action, whitening effect and UV ray shielding originated from sericin. Remaining sericin also provides less sticky feeling on sweating than conventional silk products. Furthermore, a silk yarn of the present invention can provide the knit products by using a non-sewing automatic knitting machine, which was conventionally impossible.

BRIEF DESCRIPTION OF THE DRAWINGS

[FIG. 1] A photo of the knit product according to the present invention

[FIG. 2] A magnified photo of the product of FIG. 1.

BRIEF DESCRIPTION OF THE INVENTION

Now, a core yarn to be used in the present invention is explained. A domesticated silk yarn used as a core yarn is a non-degummed yarn, wherein sericin is swollen from cocoon by boiling in reeling process at reel speed of 20 to 100 m/min, preferably reel speed of 40 to 50 m/min. For example, it is a core yarn described in JP-A-2003-202353 relevant to the invention by the present applicants and a raw silk (bave) obtained by using a reeling equipment described in JP-A-2004-312060. In the present invention, it is important that sericine in raw silk is swollen in reeling process and a raw silk is covered by the degummed wild silk yarn in the condition not to lower elongation of said raw silk. In Table 1 below, an example of relation between reel speed and reel tension is shown. As shown in Table 1, reel speed of a raw silk is usually 138 m/min and reel tension in this case is 18.5 g in Table 1, whereas at reel speed of 96 m/min in the present invention, reel tension is 8.3 g, and “not to lower elongation” means to maintain the above-described reel speed. Fineness of a raw silk obtained by such a reel condition is suitably about 42 to 84 deniers, although it depends on cloth thickness of target knit products. TABLE 1 Reel speed (m/min) 96 119 138 184 217 Reel tension (g) 8.3 11.0 18.5 15.7 16.0

As a wild silk yarn used for covering a above-described core yarn wherein sericin is in swollen state; a tussah silk yarn, a tussar silk yarn, a Mga silk yarn and the like are quoted, however, in view of cost, a tussah silk yarn is used. Reason for using a wild silk yarn is that, for example, as is clear from the fact that elongation of a tussah silk yarn is 29.3%, while elongation of a domesticated silk yarn is 23.6%, and the bave fineness of a tussah silk yarn is 6.0 deniers, while the bave fineness of a domesticated silk yarn is 3.0 deniers, a wild silk yarn has the large elongation, which makes the knitting of yarn obtained easy; and due to having larger void in fibril composing a yarn, it increases such functions of products as moisture absorption, odor absorption and adsorping function.

The next is explanation on elongation of a domesticated silk yarn used as a core yarn, and a wild silk yarn as a covering yarn; elongation of a domesticated silk yarn is 23.6% and it is 21.6% after degummed, while elongation of a tussah silk yarn is 29.3% and it increases to 36.1% after degummed (see Table in 235P of “Natural Silkworm”, co-edition by Hiroshi Akai and Sigeharu Kuribayashi, published by Science House Co., Ltd.). From these facts, knit products made of a degummed tussah silk yarn have conventionally been prevailed. On silk knit products by a domesticated silk yarn, knit fabrication is possible by using a degummed hard twisted yarn and thus knit products are widely used. However, knit products using raw silk with remaining sericin were not present because the yarn before degumming is hard and difficult to knit. In the present invention, by combination of a domesticated silk yarn with sericin in swollen state and a tussah silk yarn with large elongation, it became possible to fabricate silk knit products with sericin residence state by an automatic knitting machine. It is preferable that a tussah silk yarn after degumming is used in the present invention. As for the fineness, several yarns of about 35 deniers are used by twisting together. On fabrication of knit products, it is also possible that a cohesioned silk yarn made of only silk of the present invention is twisted together with a chemical fiber yarn.

Now a covering process is explained. In the present invention, a raw silk is used with sericine in swollen state in reeling process as a core yarn, and it is covered with a wild silk yarn in the condition not to lower elongation, that is at low reel speed of 20 to 100 m/min, and covering is executed by 200 to 600 times/m. It is usually preferable to be executed by 300 to 400 times/m. After covering, a cohesioned yarn is dried during winding to a small reel and a cohesioned silk yarn is produced by binding raw silk and a wild silk yarn by sericin and re-reeled by a common method. In a cohesioned yarn (a composite yarn) of the present invention, water-soluble sericin in reeling process is homogeneously dispersed and is adhered to bave bundle and a degummed tussah silk yarn, therefore, said yarn can express soft feeling. In this case, ratio of the bave bundle based on the degummed tussah silk yarn is preferably about 30%, which provides ratio of sericin based on the whole cohesioned yarn of about 7%. That is, too high composition ratio of the bave bundle increases ratio of sericin contained, yarn hardness increases and is not suitable to knitting.

A cohesioned yarn of the present invention can be subjected to dyeing, but due to not being subjected to degumming, sericin of a domesticated silk yarn remains in a product, which can serve to effectively utilize function such as oxidation resistance, antibacterial action, whitening effect and UV ray shielding originated from sericin. Raw silk part of yarn composing knit products is bave bundle and not twisted, which provides soft feeling to knit products.

A cohesioned yarn obtained by the following Example according to the present invention had relatively rougher touch feeling compared with a usual silk yarn, having surface gloss and fineness of 154 deniers or 294 deniers and elongation of 29.1 to 29.3%, however, was a light silk yarn without separated single filament yarn.

Using a cohesioned silk yarn of 294 deniers thus obtained, womens' three-quarter sleeve inner wear was knitted using a non-sewing automatic knitting machine (trade name of Whole Garment from Shima Seiki Mfg. Ltd.) A photo of the knit product is shown in FIG. 1 and a magnified photo of the knit surface is shown in FIG. 2. Said womens' three-quarter sleeve inner wear has sericin adhered, which reduces sticky feeling on sweating compared with conventional silk products and provides products with high commercial value, also having oxidation resistance, antibacterial action and whitening effectiveness originated from sericin. Using the same yarn, moisture maintaining gloves for sleeping time and womens' and mens' socks were knitted.

EXAMPLES

Some Examples are shown below, however, the scope of the present invention should not be limited thereto.

Using reeling equipment described in JP-A-2004-312060, and maintaining a temperature of reel releasing section of a reel tank at around 38° C., and using generally prevalent “Syunrei×Shougetsu” as bave, bave was reeled from swollen cocoon at reel speed of 50 m/min and covering was executed with a degummed tussah silk yarn while maintaining the yarn in reeling process in the condition not to add any tension. As a tussah silk yarn, a degummed tussah silk yarn on the market (from Sanka Seiren Co., Ltd.) was used.

Bave covered with a tussah silk yarn and in swollen state is dried during winding to a small reel and a domesticated silk yarn containing sericin, as a core yarn, and a tussah silk yarn for covering are fusion-bonded by sericin to provide a cohesioned yarn, which is then re-reeled.

In Table 2 below, property test results are shown on a degummed tussah silk yarn used in the present invention and a composite yarn according to the present invention obtained by covering bave in reeling process with a degummed tussah silk yarn. In the description in the Table 2, details of yarns used in each Test Example are as follows:

Test Example 1

A degummed tussah silk yarn obtained by twisting together 3 tussah silk yarns of 35 deniers, by 500 times/m.

Test Example 2

A degummed tussah silk yarn obtained by twisting together 6 tussah silk yarns of 35 deniers, by 350 times/m.

Test Example 3 The Present Invention

A composite yarn obtained by covering bave of 42 deniers with the tussah silk yarn of Test Example 1 by 400 times/m.

Test Example 4 The Present Invention

A composite yarn obtained by covering bave of 84 deniers with the tussah silk yarn of Test Example 2 by 400 times/m.

Test Example 5 The Present Invention

A composite yarn after dyeing and quelllung processing of the composite yarn obtained by Test Example 3.

Test Example 6 The Present Invention

A composite yarn after dyeing and quellung processing of the composite yarn obtained by Test Example 4.

Control Part: Conventional raw silk of 28 deniers.

In Test Example 5 and Test Example 6, dyeing was executed by a method for using a reactive dye at temperature of 40 to 70° C. and reaction time of 60 minutes, and quellung processing was executed by putting a test yarn in vacuum permeation equipment with water for sufficient absorption of water, then subjected to dewatering, dipping in a quellung agent solution at 45° C. for 120 minutes and dewatering and drying. TABLE 2 Weight Young's reduction Test Elon- Modulus rate by Ex- Yarn Fineness gation Strength (Kgf/ Degummed ample type (denier) (%) (gf/d) mm2) (%) 1 A — 36.4 3.39 487.8 0.26 2 A — 37.5 3.35 462.2 0.19 3 B 154 27.0 3.07 559.1 7.01 4 B 294 27.0 2.83 566.8 6.57 5 C 154 29.1 2.70 319.2 7.03 6 C 294 29.3 2.66 302.7 6.59 Control Raw 22.3 4.11 1185.4 22.35 silk (Note) A: a degummed tussah silk yarn B: a composite yarn of the present invention C: a composite yarn after dyeing and swelling

As is clear from the above Table, as for elongation, a degummed tussah silk yarn has elongation of about 37%, while a composite yarn after covering has low elongation of 27%, however, as shown by Test Example 5 and Test Example 6, elongation is found to increase to about 29% by quellung processing at dyeing.

As for yarn strength, reduction of strength is observed by each processing, and finally after dyeing and quellung processing it decreases to 2.6 to 2.7 (gf/d), however, yarn having strength of this level had no problem in knitting. Young's modulus of a composite yarn increases to 560 (Kgf/mm2) after covering and a little harder by adhesion of sericin, however, it became soft to 300 to 320 (Kgf/mm2) after dyeing and quellung processing and this softness and high elongation made knitting possible by an automatic knitting machine. Weight reduction rate by degumming is nearly zero in a degummed tussah silk yarn, showing nearly complete removal of sericin, however, as is clear by Test Example 3 and Test Example 4, by adhesion of sericin of bave during covering, amount of sericin increased to around 7% as the whole composite yarn. Similarly, as is clear from Test Example 5 and Test Example 6, it is observed that nearly the same amount of sericin resides and adheres even after dyeing and swelling processing.

Test results on performance of silk (cohesioned silk) according to the present invention and conventional silk, to clarify descriptions of the above Examples, are shown below. The tests were executed either on 19 August 2005 or 29 August 2005 at (foundation) Japan Spinners' Association.

a) Water Absorption Test Test item: Water absorption (A): in accordance with JIS-L-1907, an (A) method for water absorption rate. Water absorption (B): in accordance with JIS-L-1907, a (B) method for water absorption rate. Product of the present Conventional Item Classification invention product Water 49 (sec) 83 (sec) absorption rate (A) Water Wale 44 (mm) 55 (mm) absorption Course 51 (mm) 24 (mm) rate (B)

Each cloth was cut and dipped in water in a beaker to measure water absorption rate by capillary phenomenon, which results clearly show that a cohesioned silk yarn of the present invention has faster water absorption rate and is superior also in water absorption rate of knit cloth, which is estimated to be brought about because a silk yarn of the present invention is produced using a porous wild silk yarn.

b) Measurement of UV Shielding Rate Test conditions: Measurement equipment: UV-3100PC from Shimadzu Corp. Standard white board: Barium sulfate Measurement wavelength: 280 to 400 nm (total) 320 to 400 nm (A wave) 280 to 320 nm (B wave) Product of the present Conventional Item Classification invention product UV shield Total 96.9% 94.3% rate A wave 96.5% 92.5% B wave 99.0% 97.7%

Usual knit products have UV ray shielding rate of about 70 to 90% and silk is in general superior in UV ray shielding rate, however, comparing with them, knit products of a cohesioned silk yarn of the present invention is far superior in UV ray shielding rate.

(c) Deodorant Test

A test method for deodorant performance is in accordance with certification standard for deodorant fiber products and an instrumental analysis operation manual (a detecting tube method) specified by (Corp.) Fiber Evaluation Technology Association. Test Results Product of the present Conventional Item Classification invention product Deodorant Ammonia 99.0% 60.2% performance reduction rate (%)

Reason for superiority of knit products of a cohesioned silk yarn of the present invention in deodorant performance is estimated to be brought about because a silk yarn of the present invention is produced using a porous wild silk yarn.

From the above test results, it is clear that socks produced by using a cohesioned silk yarn of the present invention is significantly superior in various performances required for socks.

A cohesioned silk yarn of the present invention is composed of only silk and is a fiber not only superior in skin feeling, heat-retaining property and water absorption inherent to silk but also has, due to containing sericin, function such as oxidation resistance, antibacterial action, whitening effect and UV ray shielding originated from sericin and is possible to be widely used in products requiring such function. Furthermore, it is suitable to mass production because knit production by using a non-sewing automatic knitting machine is possible. 

1. A method for producing a cohesioned silk yarn comprising steps of, reeling a raw silk with sericin in awollen state at reel speed of 5 20 to 100 m/min; covering a raw silk containing said sericin in swollen state with a wild silk yarn; and bonding of a raw silk and a wild silk yarn by sericin.
 2. The method for producing the cohesioned silk yarn 10 according to claim 1, wherein covering with said wild silk yarn is executed by 200 to 600 times/m.
 3. The method for producing the cohesioned silk yarn according to claim 1 or claim 2, wherein said wild silk yarn is a de gummed yarn.
 4. A cohesioned silk yarn consisting of swollen raw silk as a core yarn and a wild silk yarn used to cover said core yarn and adhered to raw silk by sericin.
 5. The cohesioned silk yarn according to claim 4, wherein said swollen raw silk is raw silk in reeling process at 20 reel speed of 20 to 100 m/min.
 6. The cohesioned silk yarn according to claim 4 or claim 5, wherein said wild silk yarn is a degummed tussah silk yarn.
 7. Silk knit cloth consisting by knitting the cohesioned silk yarn according to claim 4 or claim
 5. 